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[Electron/LTE] Power Manager Watchdog Timer Fix #1581

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merged 3 commits into from Dec 5, 2018

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commented Oct 25, 2018

Problem

Modem on Electron/LTE turn off unexpectedly during initialization when powered from a USB Host only (no battery).

After an investigation it was discovered that the PMIC watchdog causes current limit to drop to 100mA temporarily which causes the modem to stop responding to AT commands.

Solution

Power Manager no longer using PMIC watchdog because it causes current limit to drop to 100mA temporarily when it expires

Workaround: For 0.8.0-rc.1 ~ 0.8.0-rc.11, add PMIC().disableCharging() to setup() when no battery is used.

Steps to Test

  1. Program an Electron with this PR's firmware
  2. Leave the battery disconnected, powered via USB only
  3. The system will check for a disconnected battery every 40 seconds
  4. The device should stay connected, AT commands should continue to work.
  5. Compared to 0.8.0-rc.11 system firmware, after 40 seconds of the battery being disconnected, the PMIC watchdog causes current limit to drop to 100mA temporarily which causes the modem to stop responding to AT commands.

References

Fixes #1548


Completeness

  • User is totes amazing for contributing!
  • Contributor has signed CLA (Info here)
  • Problem and Solution clearly stated
  • Run unit/integration/application tests on device
  • (N/A) Added documentation
  • Added to CHANGELOG.md after merging (add links to docs and issues)
[system] power manager: no longer using PMIC watchdog because it caus…
…es current limit to drop to 100mA temporarily when it expires

@technobly technobly added the bug label Oct 25, 2018

@technobly technobly added this to the 0.8.0 milestone Oct 25, 2018

@technobly technobly requested a review from avtolstoy Oct 25, 2018

@kubark42

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commented Oct 26, 2018

Nice find!

@elijthomas

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commented Dec 4, 2018

This was an issue for a customer identified on ALL there LTE devices without batteries, PMIC().disableCharging() (as mentioned above) didn't fix the issue but PMIC.disableWatchdog(); IS the fix that allows these units to continue to send and receive AT commands.

sergeuz added 2 commits Dec 5, 2018
Power manager: do not report battery charge if currently in DISCONNEC…
…TED state, do not transition from DISCONNECTED to NOT_CHARGING state immediately (backported from mesh-develop)
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commented Dec 5, 2018

I backported f87f65f and added a fix for #1557 to this branch. @avtolstoy please re-review.

@sergeuz sergeuz merged commit 8e03ae7 into develop Dec 5, 2018

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@sergeuz sergeuz deleted the fix/powermanager branch Dec 5, 2018

@technobly technobly restored the fix/powermanager branch Dec 5, 2018

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